What's Vo^1/2?

Zipper730 · Mar 6, 2020

It has to do with a chart from the F4U-1 involving improvements in speed by de-navalizing the aircraft for land-based operations. There's indicated airspeed, and there's Vo^1/2.

http://www.wwiiaircraftperformance.org/f4u/f4u-1-02334.pdf

If I had to make a shot in the dark, I'd guess it was CAS, but I don't know.

drgondog S Shortround6 W wuzak X XBe02Drvr

drgondog · Mar 9, 2020

Zipper730 said:
It has to do with a chart from the F4U-1 involving improvements in speed by de-navalizing the aircraft for land-based operations. There's indicated airspeed, and there's Vo^1/2.

http://www.wwiiaircraftperformance.org/f4u/f4u-1-02334.pdf

If I had to make a shot in the dark, I'd guess it was CAS, but I don't know.

drgondog S Shortround6 W wuzak X XBe02Drvr

I didn't see reference to Vo^1/2 but 1/2 *rho*V^2 is dynamic pressure which is directly associated with parasite Drag and CDp.

mikewint · Mar 9, 2020

In math/physics a variable like V, for example might take many forms like V sub i or Vi for initial Velocity and Vf for final velocity. Another way is to use numbers and V0 for original or starting velocity
In mathematics raising a number to the 1/2 power is the same as taking the square root of that number so 4^1/2 = 2
If your chart is dealing in statistics then there is the Square root Law: The square root law says that as the sample size (n) grows, the standard error will shrink by a factor of the square root of n. So Vo could be the number of initial velocities? sampled
In addition for a set of velocities it is useful to calculate an RMS or Root Mean Square value: 1. Square all values 2. Compute the average(mean) value for all squares 3. Take the square root of the average

Zipper730 · Mar 10, 2020

drgondog said:
I didn't see reference to Vo^1/2

It was the second line on the chart: There was

Indicated airspeed, knots
Vo^1/2, m.p.h.

but 1/2 *rho*V^2 is dynamic pressure which is directly associated with parasite Drag and CDp.

CDp is Coefficient of Drag Polar?

mikewint said:
In math/physics a variable like V, for example might take many forms like V sub i or Vi for initial Velocity and Vf for final velocity. Another way is to use numbers and V0 for original or starting velocity
In mathematics raising a number to the 1/2 power is the same as taking the square root of that number so 4^1/2 = 2

Square root of 295 is around 17.2

If your chart is dealing in statistics then there is the Square root Law: The square root law says that as the sample size (n) grows, the standard error will shrink by a factor of the square root of n. So Vo could be the number of initial velocities? sampled

This would have probably been based on numerous tests, but there were only two runs made...

In addition for a set of velocities it is useful to calculate an RMS or Root Mean Square value: 1. Square all values 2. Compute the average(mean) value for all squares 3. Take the square root of the average

Like 401, 402, 403 -> 401^2, 402^2, 403^2 -> 160801 + 161604 + 162409 -> 484814 -> 484814/3 -> 161604-2/3 -> sqrt*161604-2/3 -> 402.000829186541189?

Simon Thomas · Mar 13, 2020

The Vo 1/2 seems to be corrected airspeed. My WAG using current terminology is on Run #1 261.5 knots IAS -> 295 mph CAS -> 431 mph TAS.

Joe Broady · Mar 16, 2020

Zipper730 said:
It has to do with a chart from the F4U-1 involving improvements in speed by de-navalizing the aircraft for land-based operations. There's indicated airspeed, and there's Vo^1/2.

http://www.wwiiaircraftperformance.org/f4u/f4u-1-02334.pdf

Surely that number is EAS (equivalent airspeed). If you enter altitude and true airspeed from run #1, EAS matches the mystery number. Run #2 is hard to read due to the watermark going right over the numbers, but my best guess is also consistent with EAS. Due to compressibility, CAS is greater than EAS and doesn't match.

airspeed calculator

wuzak · Mar 17, 2020

Zipper730 said:
It was the second line on the chart: There was

Indicated airspeed, knots

Vo^1/2, m.p.h.

CDp is Coefficient of Drag Polar?

I don't think it is Vo^1/2, but rather Vo 1/2 (as in superscript, not to the power of). As in corrected speed, refer to notes 1 and 2 on the next page.

CDp, I would assume, is flat plat drag coefficient.

What's Vo^1/2?

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